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Denon 951

When I had my 961's serviced by a third party they returned them to me "fixed" with an error 85. I was so angry I sent them to Denon for repair and demanded my money back from the other vendor. They told me it has something to do with an internal ground.

I don't know how accurate that description really is, since they should have returned my units in working order, but that is what I was told when I had two players reworked.
 
Howdy PoB:

I recall the 85 code had something to do with optic failure.

Some years ago I came across a procedure that someone posted online for aligning the optics on the Denon CD units. Their claim was that most "optic failures" were really caused by poor tracking alignment, and that the procedure in the manual was basically useless. They had a procedure that involved marking up a CD and using it to generate an error signal that would cause the optic servo to make a "skipping" noise. The idea was to adjust the little pots to minimize the noise.

I tried it and it seem to work pretty well. I managed to not have to replace many optics on the things. There should still be a hard copy of this somewheres in your files.
 
Aligning those things. Ugghh
Spent many hours doing it “by the book” until someone showed me the damaged CD trick!
Most of the time when getting a fatal error, replacing the optics was the only thing that would fix it. Just make sure you get rid of that solder bridge anti-static safety short before trying to aligning it.
Also had a pair of Denon consumer units that had the same optic head as the 951.
 
The repetitive failures I've seen on DNF-951s are the upper spindle bearing (develops sideplay), the flat cable bewteen the pickup and the circuit biard (eventually flexing cracks the conductors and they become noisy) and the optical pickup.
NAB used to sell a pair of test CDs which were manufactured with specific defects in them... these are invaluable in aligning the optical pickup. As the poster above says, rock the pots for pickup in the worst tracks it's capable of. If you look for the pickups by googling the part number (Sony something or other, stamped on the pickup) you can often find them around $50.
Keeping the grot which accumulates on the slide part of the tray also helps. Make usre the platter has the proper end play as well.
We had some from the 90s (thewy're dated on the top) which still perform well today. Good players.
 
I believe that error code happens when servos don't lock so the player can't read the disc.
Dirty optical pickup, tracking or focus gain that is out of range are likely causes.
Contrary to what somebody else suggested, the alignment in the service manual is not useless. It is excellent and accurate. All Denons seem to be very good in this regard. The last Pioneer stable platter CD that I tried to align had a procedure in the manual that was truly useless and not obtainable. For that CD player I bought this excellent distressed CD: http://www.digital-recordings.com/cdcheck/cdcheck.html

It will let you center up the tracking gain and the focus gain but likely not as good as using the 'scope and oscillator as in the Denon manual.
 
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